System of control for electric motors.



A. 0. EASTWOOD.

SYSTEM OF CONTROL FOE ELECTRIC MOTORS.

APPLICATION FILED MAY 9, 1908.

904,765. Patented Nov. 24, 1908.

a- SEBETS-SKEET 1.

WITNESSES: INVENTOR A. C. EASTWOOD. SYSTEM OF CONTROL FOR ELECTRICMOTORS.

APPLIGATION FILED MAY 9, 1908.

Patented Nov. 24, 1908.

3 SHEETS-SHEET 2.

WI'TNE E5551 IINVENTOR Q [Ll (W- A-r-roansv A. G. EASTWOOD. SYSTEM OFGONTRQL FOR ELECTRIC MOTORS. APPLICATION FILED MAY 9, 1908.

904,765. Patented Nov. 24, 1908.

3 SHBETSS EEET 3.

WTNEQSES: I a CI FINVENTR AT'I'O R N BY ARTHUR O. EASTWOOD, OFCLEVELAND, OHIO SYSTEM OF CONTROL FOR ELECTRIC MOTORS.

Specification of Letters Patent.

Patented Nov. 24, 1908.

Application filed May 9, 1908. Serial No. 431,902.

To all whom it may concern:

Be it known that I, ARTHUR C. Essrwooo, a citizen of the United States,residing at Cleveland. in the county of Cuyahoga and State of Ohio. haveinvented or discovered new and useful Improvements in Systems of Controlfor Electric Motors, of which the followi g is a specification.

My invention relates'to a improved system of control for electricmotors.

The objects of my invention are: To prevent excessive rush of currentwhen a manually operated controller is advanced to the full-speedposition very 'apidly; to prevent injurious rush of current when anelectric motor is suddenly reversed by means of a manually operatedcontroller; to protect the motor governed by the controller fromexcessive overload without opening the circuit of the motor; to securethe above mentioned results with a controller which will be simple andrelatively inexpensive.

\Vhen a manually operated controller is used to govern an electricmotor, if the con trolling resistance is cut out too rapidly by theoperator, an excessive current will flow through the motor. If the motoris sad denly reversed, while running at full speed, a still greaterexcess of current is likely to result.

- My invention embraces means for limiting the flow of curret and thusguarding against the inexperience or carelessness of an operator whenthe controller is too rapidlyadvanced to the full speed position or toosuddenly reversed.

My invention also embraces means for automatically limiting the flow ofcurrent when the load becomes excessive, even after all of theresistance co trolled by the man-- f motor circuit may be varied at thewill of circuit. At or near the full-on position of the manuallyoperated controller, I provide switch contacts and connections at whichthe energizing circuit of the power actuated switch or switches isnormally open till the manually operated controller is advanced to, ornearly to, the full speed position. In ad dition to these switchcontacts I provide a second set of switch contacts controlled by meansrts onsive to the current flowing through the motor, 1 et'erably by arelay having its winding directly in series with the motor circuit. Therelay will be so arranged and adjusted that it the current flowingthrough the motor exceeds a predetermined amount the contacts controlledby the relay will be separated, thereby holding the energizing circuitof the power-actuated switch orswitches open; while if the currentflowing in the motor circuit is less than a predetermined amount thecontacts controlled by the relay will be in engagement. \Vith thisarrangement of parts, no matter how rapidly the resistance governed bythe manually operated controller may be cut out the current will belimited by the supplementary or current-limiting resistance. Thesupplementary resistance may be proportioned to limit the current to,say, a 50% overload on the motor. The current controlled relay may beadjusted to prevent cutting out of the supplementary resistance by thepower-actuated switch till the motor current has dropped to a full-loadvalue. In cases where the character of the load is such that. thesupplementary resistance cannot be cut out as a unit by a singlepower-actuated switclrthe resistance will be divided into sectionslandcontrolled. by two or more power-actuated switches, governed by thecurrent-controlled relay.

My invention will be more fully understood by reference to theaccompanying drawings in which Figure 1 is a diagram of electricalconnections of one form of my invention; Fig. 2, a modification of Fig.1; and Fig. 3, a second modification in which the supplementaryresistance is divided into two sections and two magnetically operatedswitches are provided to control the resistance.

In Fig. 1, M is a manually operated controller of the well known dial orfaceplate type. R and R are resistances under the control of thecontroller M. The resistances are divided into sections connected to thecontact segments in the groups r and 1' 1' and r. The contact segmentsin the group 1' are electrically connected to corresponding segments inthe group 1' and the segments in group 9* are electrically connected tocorresponding segments in the group 1*. a and a are contact segmentsarranged concentrically with the outer groups 1", 1, 1' and 1 0 and care additional Iwhich the arm is moved from the ofi'-position., in whichit is shown. The brush m is similarly adapted to engage with thesegments 0 or 0 and the brush m with the segments a or (L The other endof the arm m, is provided with brushes m and m, the brush m beingadapted to cooperate with the se 'ments a and a and the brush m with t egroups of segments 1" and 9 (Z, d, cl, (Z are dead-blocks (having noelectrical connections) upon which the brushes rest when the contact armm, is in the cit-position. S is a switch connected to the source ofcurrent. A isthe armature of the motor to be controlled and F is itsseries field winding. L is the supplementary or currentlimitingresistance. S is a magnetically operated switch, adaptedwhen closed toshortcircuit the resistance L. O is a currentcontr'olled relay havingcontacts controlling the circuit of the actuating winding of the switchS. The parts are indicated in the relations which they take when thecontroller M is in the oif-position. If the operating lever m of thecontroller be moved in a clockwise direction till the brushes m and mmake contact with the first live segments in the groups 1." and 1'respectively, a circuit will be completed through the motor as follows:from the positive side of the switch S through the wires 1 and 2, theseries field F, the supplementary resistance vL, the windingof the relay0, the wire 3 and, the cross connection 5, through all of the resistanceR the cross-connection 6 to the first live segment in the group 1',thence through the brush m to the brush m, the segment (1*, the wire 7the armature'A, the wire 8, the segment a, the brush m to brush m', tothe first live segment in the group 1", through the wire 9, all of theresistance R, the connection 10, and the wire 11 to the negative side ofthe ,switch S, thus completing the circuit. In this position of thecontroller all of the resistances R and R governed by the controller M,as well as the supplementary resistance L, is in series with the motorwhich will therefore operate at minimum speed. As the arm of thecontroller is moved further in a clockwise direction the sections of theresistances R and R are consecutively cut-out in a well-known manner. Nomatter how rapidly the operator may move the arm m to cut-outtheresistancesR and R the maximum flow of current is limited by the Iresistance L.

tions and that the operator has so operated the ,controller M that thisvalue of current is reached when the arm m reaches the full-on position.Vewill assume also that the relay O is adjusted to raise the plunger andlift the contactmember 0 from the contacts o and 0 when the currentthrough its winding rea ches a value corresponding to the fullloadcurrent of the motor. Under the conditions assumed the contacts of therelay 0 will be thus separated when the full-on position of,thecontroller is reached. As the controller arm m reaches the full-onposition, the brush m makes contact with the segmentrf, which tends tocomplete a circuit through the windingC, of the switch S.

' plunger of the relay 0 will fall, thus causing -the contact member 0to connect the contacts 0 and 0 The circuit through the actuatingwinding of the switch S is then completed as follows :from the positivesidetofthe switch S, through the wires 1 and 12, the contacts 0 and oand 0 of the relay 0, the winding 0 of the switch S, the wire 13 tocontact 0 through brushes m and MP, the cross-connection 10 and the wire11 to the negative side of the switch S. This cir- 'cuit energizes thewinding C causing it to draw in its plunger, thus closing the switch Sat its contacts a and 8 As will be readily seen this short-circuits theresistance L which permits the motor to come up to full s eed. If, whilethe motor is running at ull speed its load should increase beyond anormal amount the relay will raise its plunger, thus opening the circuitof the coil C at the contacts 0, 0 and 0 and causing the switch S toopen, thus reinserting the resistance L in the motor circuit. When theoverload has disappeared, the relay will again drop its plunger, causingthe resistance L to be again automatically cut-out;

When the arm m is moved toward the oftrotation to be reversed.

step by step. a counter as above current will flow through thearn'iaturc A in creed direction, causing its direction of If the motorbe pluggedlby suddenly reversing the controller the resistance L will bein circuit to prevent an excessive rush of current.

Fig. 2 isidentical with Fig. 1 with the exception that the connectionsto the switch S are such that when the switch closes it shortcircnitsboth the resistance L and the wind ing' of the relay 0. In this case therelay becomes inoperative after the switch S has closed until thearin ofthe controller is again moved from the full-on position.

Fig. 3 differs from Fig. 1 in that the cur-- rent-limiting resistance isdivided into two sections L and L and two magnetically operated switchesS and S are provided for controlling this resistance. The main or seriesconnections between the manually operated controller M, the armature andfield of the motor and the winding of the relay 0 are the same in eithercase. In Fig. 3 if the lull-on position of the controller is reached,and an over-load does not exist, the circuit of the actuating" windingof switch S will be completed as follows :from the positive side of theswitch S through the wires 1 and 12, the winding of the switch S". thewire 14, the contacts 0 0, and 0 of the relay 0, the wires-15 and 17 tothe contact c'- or o"- as the case may be, through the brushes m and mand the wires 10 and 11 to the negative side of switch S. This causesswitch S to close, short-circuiting the section of the resistance L twocontact members as and 3 adapted to bridge respectivelyeontacts 00 m andy y when the switch is closed. The upper end of the winding oi switch .8is connected to contact 02 through the resistance "r, and contact (c iscom'tected by wire 17 to wire 19 ahead of the contacts of the relay 0.lVhen switch S is once closed it thereioreyremains closed with theresistance in series with its winding as long as the arm of thecontroller is in the full-on position. irrespective of future action ofthe relay 0. The; resistance "r is so proportioned as to allowSllfillZifil-lft current to flow through the winding of'rhe switch S tohold the switch closed but limits the current to a value below thatrequired to close the switch S The switch F cannot close till the switch3 has closed because the upper end of its winding is connected to wire14- throue'h the wire 18 and the contacts 7 y. and 9/ con rol ed by theswitch Fl. lt. when the swi ch closes. an overload occurs thron -h shor-circuitino he resistance L. the relay 0 will raise'its plunger andtheswitch S cannot close until the cur- The plunger of the switch Scarries rent has again dropped to normal value"; at which time thecircuit through the winding of switch S -ill be as follows :from thepositive side of the switch S, the wires 1 and 12, the winding of theswitch S, the wire 18, the switch contacts y, and 7 the wire 14, therelay contacts 0, 0, and 0 the Wires 15 and 19, the contact or c as thecase may be, the'brush m to the brush m and the wires 10 and 11. to thenegative side of the switch S. The winding of switch FF is thusenergized and the switch closes.

short-circuitin the resistance L and pc.r mitting the motor to come upto iiull speed. it an overload occurs when the motor is run= ninp; atfull speed the relay will raise its plunger thus opening the circuit ofthe coil of switch S at the relay contacts, causingswitch S to open andthus rcinsert the resistance L in the motor circuit. .Vhen the overloadis removed the relay will drop its plunger. thus causing'switch S toagain close automatically. When desirable the .connections to switch Smay be so made that the switch. when closed. short-circuits both theresistance L and the winding of the relay 0 (as in Fig. Ql thusrendering the relay inoperative after switch S is closed.

l'Vhile I have illustrated my invention in connection with a reversingcont oller of the face-plate type and a series wound motor. I do notwish to limit my invention to these precise. forms of apparatus sincecontrollers and motors of other types can be substituted withoutdenartina' from the soirit of my invention. The relay 0 likewise.instead of beino arran ed as I have shown it with its winding; in serieswith the motor circuit. may he arran ed in other ways. the requirementbeing that its action be Q'oyerned by the a ount of current. taken bythe motor.

. I claim- A 1. In a controller for electric motors, a resistance inseries with the main motor cir cuit. a manual controller therefor, asecond resistance in series with the said main motor circuit. and meansfor automatically short circuiting said second resistance, said shortcircuiting means being operative only when substantially all of saidfirst mentioned resistance is cut out by said manual controller.

2. In a control system. an electric motor. two resistances arranged inseries in the main circuit of said motor. a manual controller hayingmoving contac s for governi112 one of the resistances. and meansgoverned both by the position of the moving contacts of said manualcontroller and by the current. fl wing throuo'h the motor forcontrolling said s cond resistance.

3. ln a controller for an electric motor. a manually onerated s i ch forreversing said motor and for controlling its acceleration up to acertain point in either direction, and

automatic means for controlling the completion of the acceleration ineither direction, said automatic means acting to complete theacceleration only when the manually operated switch is inthe full speedposition and i when the current flowing through the motor is less than apredetermined value.

4:. In a control system for an electric motor, a manually operatedcontroller, a current limiting resistance in addition thereto, saidcurrent limiting resistance. being in vseries with the main motorcircuit, when the .manually operated controller is in any but the fullspeed position, and means for short circuiting said current limitingresistance only when said manually operated controller is in its, fullspeed position, and the current flowing-through the main motor circuitis less than a predetermined value.

5. In an electric controller, a motor, a resistance in the motorcircuit, means under the control of the operator for cutting out saidresistance, a second resistance inthe 'motor' circuit, and meanspreventing the operator from cutting out the second resistance unlessthe current in the motor circuit is below a predetermined value.

6. In an electric controller, a motor, a resistance in the motorcircuit, means under the control of the operator for cutting out.

short-circuiting the second resistance, a switch having contacts at ornear the full-on position of the said controller, a second" switch, anda relay controlled by the motor current and controlling the said secondswitch, said relay having contacts for clos-- ing the said second switchwhen the motor current falls below a predetermined value and for openingsaid second switch when the motor current rises above a predeterminedvalue.

8. In an electric controller, a motor, a resistance in the motorcircuit, a manually operated controller for governing the resistance, asecond resistance in the motor circuit, a magnetically operated switchfor short-cir cuiting the second resistance, a switch hav ing contactsat or near the full-on position of the said controller, a second switch,and -a relay controlled by the motor current and controlling the saidsecond switch, said relay having contacts for closing the said secondswitch when the motor current falls below a predetermined value and foropening said second switch when the motor current rises above apredetermined value, the last two switches being in series with thewinding of the said magnetically operated switch.

'9. In an electric controller, a motor, a resistance in the motorcircuit, a manually-operated controller goveruing the said resistance,an additional resistance in the motorcircuit, a magnetically-operatedswitch for controlling the additional resistance, and a contact at ornear the full-on position of the ;said controller through which theclosin mechanism of said magnetically-operate switch may be energized.

Signed at Cleveland, Ohio, this 7th day of May, A. D. 1908. v ARTHUR C.EASTl/VOOD. Witnesses:

H. M. DIEMER, F. R. FISHBACK.

